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Why Choose Sil-Pad Thermally Conductive Insulators?

Overview Polyimide Films

The Bergquist Company established the standard for elastomeric, thermally conductive insulation materials with the development of Sil-Pad over 25 years ago.Sil-Pad was developed as a clean,grease- free alternative to mica and grease.Now,a complete family of materials is available to meet the diverse and changing requirements of today’s design engineer. Polyimide films can also be used as insulators and are often combined with wax or grease to achieve a low thermal impedance.These polyimidefilms are especially tough and have high dielectricstrength.Sil-Pad K-4,K-6 and K-10 incorporate polyimide film as the carrier material.

Mica and Grease

Mica insulators have been in use for over 35 years and are still commonly used as an insulator.Mica is inexpensive and has excellent dielectric strength,but it is brittle and is easily cracked or broken. Because mica used by itself has high thermal impedance,thermal grease is commonly applied to it.The grease flows easily and excludes air from the interface to reduce the interfacial thermal resistance.If the mica is also thin (2-3 mils [50-80 µm]),a low thermal impedance can be achieved.However,thermalgrease introduces a number of problems to the assembly process.It is time-consuming to apply,messy and difficult to clean.Once thermal grease has been applied to an electronic assem- bly,solder processes must be avoided to prevent contamination of the solder.Cleaning baths must also be avoided to prevent wash-out of the interface grease,causing a dry joint and contamination of the bath.Assembly, soldering and cleaning processes must be performed in one process while the greased insulators are installed off-line in a secondary process.If the grease is silicone-based,migration of silicone molecules occurs over time,drying out the grease and contaminating the assembly. Silicone migration onto electrical contacts can result in the loss of electrical conductance.For this reason,silicone-based thermal grease has not been used in telecommunications systems.

Ceramic Insulators

Other insulation materials include ceramic wafer insulators which have a higher thermal conductivity than mica.They are often used thicker (20-60 mils),(.5 to 1.5 mm) to reduce capacitive coupling while maintaining a low thermal impedance.Drawbacks to ceramic insulators are their high cost and,like mica,they are rigid and crack easily.Also,ceramic beryllia use requires careful handling since inhalation of beryllia dust can cause lung inflammation (berylliosis).
SIL-PAD 48